Re: RX of uBITx V3 fried - which components to change? #ubitx

Jerry Gaffke
 

Yes, on the uBitx, K1-14 is shorted to ground for DC by T2 pins 1 and 6 by way of L1,L2,L3,L4.
At DC, T2,L1,L2,L3,L4 are all just a few centimeters of magnet wire, and present very little resistance.
At an RF frequency of 3.5mhz and more where our ham bands are, they present significant impedances.

Jerry, KE7ER



On Sun, Jun 9, 2019 at 05:26 PM, Sascha Bohnet | DL5SMB wrote:

So I am at home again and the troubleshooting begins :-)

Maybe thats's a stupid question, but should there be a DC short within the antenna line between the relais K1 (14) and ground in the signal path?

I first thought Q3 in ND6DTs AGC was dead as I had a short between Ground and RF-Out. I then replaced it and noticed hat that did not help and Q3 had again a short between Source and Drain.

So i took took out the AGC, tried to find the problem on the small PCB and noticed that the short (about 3 Ohm) was in fact on the uBITX itself. I am a bit bad at reading schematics,
but then i found T2, where the signal path 1 is connected to 6 GND . So this is normal beaviour, am I correct?

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